Telecommunications Cable Jacket Adapted for Post-Extrusion Insertion of Optical Fiber and Methods for Manufacturing the Same

ABSTRACT

The present disclosure relates to a telecommunications cable having a jacket including a feature for allowing post-extrusion insertion of an optical fiber or other signal-transmitting member. The present disclosure also relates to a method for making a telecommunications cable having a jacket including a feature for allowing post-extrusion insertion of an optical fiber or other signal-transmitting member.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 11/757,680,filed Jun. 4, 2007, which is a continuation of application Ser. No.11/056,380, filed Feb. 11, 2005, now U.S. Pat. No. 7,225,534, whichapplications are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates generally telecommunications cable fortransmitting data and to methods for manufacturing telecommunicationscable.

BACKGROUND

A fiber optic cable typically includes: (1) a fiber or fibers; (2) abuffer or buffers that surrounds the fiber or fibers; (3) a strengthlayer that surrounds the buffer or buffers; and (4) an outer jacket.Optical fibers function to carry optical signals. A typical opticalfiber includes an inner core surrounded by a cladding that is covered bya coating. Buffers typically function to surround and protect coatedoptical fibers. Strength layers add mechanical strength to fiber opticcables to protect the internal optical fibers against stresses appliedto the cables during installation and thereafter. Example strengthlayers include aramid yarn, steel and epoxy reinforced glass roving.Outer jackets provide protection against damage caused by crushing,abrasions, and other physical damage. Outer jackets also provideprotection against chemical damage (e.g., ozone, alkali, acids).

It is well known that micro-bending of an optical fiber within a cablewill negatively affect optical performance. Shrinkage of the outerjacket of a fiber optic cable can cause axial stress to be applied tothe optical fiber, which causes micro-bending of the optical fiber. Onecause of jacket shrinkage is thermal contraction caused by decreases intemperature. For example, fiber optic cables are typically manufacturedusing an extrusion process. After a given cable has been extruded, thecable is passed through a cooling bath. As the cable cools, the jacketcan contract more than the internal optical fiber or fibers causingmicro-bending of the fiber or fibers.

SUMMARY

One aspect of the present disclosure relates to a telecommunicationscable having a jacket including a feature for allowing post-extrusioninsertion of an optical fiber or other signal-transmitting member.

Another aspect of the present disclosure relates to a method for makinga telecommunications cable having a jacket including a feature forallowing post-extrusion insertion of an optical fiber or othersignal-transmitting member.

A variety of other aspects are set forth in the description thatfollows. The aspects relate to individual features as well as tocombinations of features. It is to be understood that both the foregoinggeneral description and the following detailed descriptions areexemplary and explanatory only and are not restrictive of the inventionas claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of an example fiber optic cable inaccordance with the principles of the present disclosure, thecross-section is taken along section line 1-1 of FIG. 12;

FIG. 2 illustrates an example system for extruding the fiber optic cableof FIG. 1;

FIG. 3 is a cross-sectional view taken along section line 3-3 of FIG. 2;

FIG. 4 is a cross-sectional view taken along section line 4-4 of FIG. 2;

FIG. 5 shows an example crosshead that can be used with the system ofFIG. 6;

FIG. 6 is a side view of a die used with the crosshead of FIG. 5;

FIG. 7 is a top view of the die of FIG. 6;

FIG. 8 is an end view of the die of FIG. 6;

FIG. 9 is a side view of a tip used with the crosshead of FIG. 5;

FIG. 10 is an end view of the tip of FIG. 9;

FIG. 11 is a top view of the tip of FIG. 9;

FIG. 12 shows an example system for inserting optical fiber into thecable extruded at the system of FIG. 2;

FIG. 13 is a cross-sectional view taken along section line 13-13 of FIG.12;

FIG. 14 is a cross-sectional view taken along section line 14-14 of FIG.12;

FIG. 15 is a cross-sectional view of another example fiber optic cablein accordance with the principles of the present disclosure;

FIG. 16 is a cross-sectional view of an example crosshead used toextrude the fiber optic cable of FIG. 15;

FIG. 17 is a cross-sectional view taken along section line 17-17 of FIG.16; and

FIG. 18 is a cross-sectional view taken along section line 18-18 of FIG.16.

DETAILED DESCRIPTION

The present disclosure relates generally to telecommunication cablejackets having features that facilitate the post-extrusion insertion ofoptical fibers into the jackets. Example features that facilitate thepost-extrusion insertion of optical fibers include slits, predefinedslit locations (e.g., perforations, partial slits, weakened regions,etc.). In certain embodiments, a ripcord can be pulled from a jacket tocreate a feature that facilitates the post extrusion insertion ofoptical fiber into the jacket. The present disclosure also relates tomethods for manufacturing jackets having features for facilitating thepost extrusion insertion of optical fibers, and also relates to methodsfor inserting optical fibers into jackets. While the various aspect ofthe present disclosure are particularly useful for fiber optic cables,the aspects are also applicable to other types of telecommunicationscables (e.g., copper cables).

FIG. 1 illustrates an example fiber optic cable 20 in accordance withthe principles of the present disclosure. The fiber optic cable 20includes an optical fiber 22, a strength structure 26 (e.g., one or morereinforcing members or layers), an optional filler 27 and a jacket 28.The jacket 28 includes an interior passage 31 (e.g., a hole) that runsalong the length of the jacket 28. The optical fiber 22 is positionedwithin the interior passage 31. The jacket 28 also includes a slit 29that runs along the length of the jacket for allowing the post-extrusioninsertion of the optical fiber 22 into the interior passage 31 of thejacket 28. The jacket 28 further includes an interior passage 33 thatruns parallel to the passage 31 for holding the strength structure 26.

It will be appreciated that the optical fiber 22 can have any number ofconventional configurations. For example, the optical fiber 22 mayinclude a silica-based core surrounded by a silica-based cladding havinga lower index of refraction than the core. One or more protectivepolymeric coatings (e.g., ultraviolet curable acrylate) may surround thecladding. The optical fiber 22 may be a single-mode fiber or amulti-mode fiber. Example optical fibers are commercially available fromCorning Inc. of Corning, N.Y. While only one fiber 22 is shown withinthe jacket 28, in other embodiments multiple fibers can be mountedwithin the jacket 28.

The fiber 22 is preferably an unbuffered fiber. However, buffered fiberscould also be used. For example, the buffers can be made of a polymericmaterial such as polyvinyl chloride (PVC). Other polymeric materials(e.g., polyethylenes, polyurethanes, polypropylenes, polyvinylidenefluorides, ethylene vinyl acetate, nylon, polyester, or other materials)may also be used.

The strength structure 26 is adapted to inhibit axial tensile and/orcompressive loading from being applied to the optical fiber 22. Thestrength structure 26 preferably extends the entire length of the fiberoptic cable. In certain embodiments, the strength structure can includeone or more reinforcing members such as yarns (e.g., aramid yarns),fibers, threads, tapes, films, epoxies, filaments, rods, or otherstructures. In a preferred embodiment, the strength structure 26includes a reinforcing rod (e.g., a glass reinforced plastic rod havingglass rovings in an epoxy base, a metal rod, a liquid crystal polymerrod, etc.) that extends lengthwise along the entire length of the cable.

The filler 27 is optional and functions to fill void areas within thejacket. The filler 27 would typically be used for cables designed forenvironments where water intrusion is a concern. By filling the voidsaround and between the fibers, the filler prevents water from enteringthe voids. Example fillers include thixotropic gels, petrolatumcompounds. In certain embodiments, the filler can have adhesiveproperties that assist in sealing the slit and in holding the slitclosed after the fiber has been mounted within the jacket.

The slit 29 allows the jacket 28 to be spread-apart to allow the fiber22 to be inserted within the interior passage 31 of the jacket 28. Afterinsertion of the fiber 22 into the passage 31, the slit can be heldclosed by the inherent mechanical properties of the jacket, which biasthe slit to a closed position. Additional structure can also be used toassist in holding the slit 29 closed after insertion of the fiber. Forexample, adhesives or other bonding agents can be used to bond togetherthe opposing portions of the jacket that define the slit 29. In otherembodiments, a reinforcing sheath can be mounted over the jacket 28after insertion of the optical fiber to prevent the slit from opening.

The jacket 28 is preferable manufactured from an extrudable basematerial such as an extrudable plastic material. Example base materialsfor the jacket include conventional thermoplastic polymers such asAlcryn® Melt-Processible Rubber sold by Advanced Polymer Alloys (adivision of Ferro Corporation), polyethylene, polypropylene,ethylene-propylene, copolymers, polystyrene, and styrene copolymers,polyvinyl chloride, polyamide (nylon), polyesters such as polyethyleneterephthalate, polyetheretherketone, polyphenylene sulfide,polyetherimide, polybutylene terephthalate, low smoke zero halogenspolyolefins and polycarbonate, as well as other thermoplastic materials.Additives may also be added to the base material. Example additivesinclude pigments, fillers, coupling agents, flame retardants,lubricants, plasticizers, ultraviolet stabilizers or other additives.The base material can also include combinations of the above materialsas well as combinations of other materials.

FIG. 2 illustrates a system 100 for extruding the fiber optic cable 20of FIG. 1. The system 100 includes a crosshead 102 that receivesthermoplastic material from an extruder 104. A hopper 106 is used tofeed materials into the extruder 104. A conveyor 108 conveys thematerial for the jacket 28 to the hopper 106. The extruder 104 is heatedby a heating system 112 that may include one or more heating elementsfor heating zones of the extruder as well as the crosshead to desiredprocessing temperatures. A rip member 115 (see FIGS. 2 and 3) is fedinto the crosshead 102 from a feed roll 114. The rip member 115 ispreferably a cord, strip, string, fiber or other elongated structureconstructed of one or more component parts. Example materials formanufacturing the rip member 115 include aramid yarn, metal wire,polypropylene, extruded glass rod or other materials. A strengthstructure 26 (see FIGS. 2 and 3) is also fed into the crosshead from oneor more feed rolls 116. A water trough 118 is located downstream fromthe crosshead 102 for cooling the extruded product (see FIG. 4) thatexits the crosshead 102. The cooled final product is stored on a take-uproll 120 rotated by a drive mechanism 122. A controller 124 coordinatesthe operation of the various components of the system 100.

Referring to FIG. 5, the extruder 104 is depicted as including anextruder barrel 140 and an auger/style extruder screw 142 positionedwithin the barrel 140. An extruder screen can be provided at the exitend of the extruder 104. The screen prevents pieces too large forextrusion from passing from the extruder into the crosshead 102.

Referring still to FIG. 5, the crosshead 102 includes a jacket materialinput location 200 that receives thermoplastic material from theextruder 104. A tip 202 (shown at FIGS. 5 and 9-11) and a die 204 (shownat FIGS. 5-8) are mounted at the crosshead 102. The tip 202 defines afirst inner passageway 206 through which the rip member 115 is fed. Thetip 202 also defines a second inner passageway 207 through which thestrength structure 26 is fed. The second inner passageway is spacedbelow and generally parallel to the first inner passageway. The die 204defines an annular extrusion passage 208 that surrounds the exterior ofthe tip 202. The crosshead 102 defines an annular passageway 209 forfeeding the thermoplastic jacket material from the extruder 104 to theannular extrusion passage 208. Within the crosshead, the flow directionof the thermoplastic material turns 90 degrees relative to the flowdirection of the extruder 104 to align with the direction of travel ofthe strength structure 26 and the rip member 115.

Referring to FIGS. 6-8, a slitting blade mount 220 is coupled to the die204. The slitting blade mount 220 includes a pair of mounting plates 221separated by a space 222 for receiving a slitting blade 223 (shown atFIG. 5). Fasteners such as screws or bolts can be inserted throughopenings 225 in the plates 221 to secure the blade 223 between theplates 221.

As shown at FIG. 5, the slitting blade 223 is mounted directly at theexit of the annular extrusion passage 208. As depicted, the blade 223extends to the exterior surface of the rip member 115 so as to cut aslit that extends completely from the exterior of the jacket to the ripmember 115. However, in other embodiments, the blade may extend only apartial distance between the exterior of the jacket and the exterior ofthe rip member 115.

In use of the system 100, the base material for the jacket and anyadditives are delivered to the hopper 106 by the conveyor 108. From thehopper 106, the material moves by gravity into the extruder 104. In theextruder 104, the material is mixed, masticated, and heated. Theextruder 104 also functions to convey the material to the crosshead 102,and to provide pressure for forcing the material through the crosshead102. As the material exits the crosshead 102, the material is forcedbetween the tip and the die causing the material to be formed to adesired cross-sectional shape. For example, the material is formed withthe passages 31, 33 (see FIG. 4) in which the strength structure and therip member are positioned. After passing between the tip and the die,the material is cut/slit by the slitting blade 223. Because the materialis still relatively molten when cut, the surfaces defining the slit mayadhere slightly back together after being slit. However, at the veryleast, the slitting blade provides a weakened region (i.e., apre-defined slit location) corresponding to the slit.

The extrusion process can be a pressure or semi-pressure extrusionprocess where product leaves the crosshead at the desired shape, or anannular extrusion process where the product is drawn down afterextrusion. After cooling, the product is collected on the take-up roller120.

FIG. 12 shows an example system 320 for inserting optical fiber (orother type of signal conveying member) into the cable extruded at thesystem of FIG. 2. The system 320 includes a rip member removal station322 and a fiber insertion station 324. Before the cable from the systemof FIG. 2 is processed at the system of FIG. 3, it can be cycled throughtemperature variations to remove internal stress from the jacketmaterial.

Referring to FIGS. 12 and 13, the system 320 includes two sets of pinchrollers 326 that assist in moving the cable through the optical fiberinsertion station 324. The cable is pinched between the rollers 326 andthe rollers are driven to control the position of the cable. Feed andtake-up rollers 328, 329 also assist in controlling the position of thecable.

The rip member removal station 322 includes a driven roller 330 thatpulls the rip member 315 from the cable as the cable is moved throughthe system 320.

As the rip member 315 is removed from the cable, the jacket of the cabletears/rips along the pre-defined slit location thereby breaking anybonds between the opposing walls of the slit that may have occurredafter the slitting process. In alternative embodiments, the removal ofthe rip member 315 may be a manual process.

The optical fiber insertion station 324 includes a spreading shoe 340(see FIG. 14) having a spreader 342 (e.g., a v-shaped plow or otherstructure having angled surfaces/ramps) that spreads apart the slit inthe cable as shown at FIG. 14. The insertion station 324 also includesan insertion tool 344 that receives optical fiber from an optical fiberfeed roll 346. The insertion tool 344 includes an angled receivingportion 348 and a bent tip 350. The bent tip 350 fits through the slit29 and into the passage 31 of the cable. The tip 350 preferablyco-axially aligns with the passage 31 of the cable jacket. A pair ofpinch rollers 360, 362 pushes the optical fiber into the insertion tool344. The optical fiber is frictionally pinched between the rollers 360,362. The rollers 360, 362 are driven by a drive roller 363 that engagesthe cable being processed by the system. Movement of the cable causesrotation of the drive roller 363 that, in turn, causes rotation ofrollers 360, 362. This feed configuration ensures that the optical fiberand the cable are fed though the system at the same linear speed.

The optical fiber insertion station 324 also includes an optional fillerinjection tool 366 for injecting filler into the passage 31. As shown atFIG. 12, the tool 366 includes a syringe having a needle that extendsinto the passage 31 through the slit 31. In other embodiments, anadhesive application station could be placed downstream of the fillerinjection tool 366 to apply adhesive to the jacket for the purpose ofsealing and bonding the slit closed. In still other embodiments, asheathing station can be placed downstream of the insertion station forapplying an outer sheath about the jacket for protecting the jacket andfor holding the slit closed.

In use, the cable is fed from feed roller 328 and moved through thesystem in a controlled manner by rollers 326. At the rip member removalstation 322, the rip member 315 is torn from the jacket to ensure thatthe slit is fully open. Thereafter, at the fiber insertion station 324,the slit is spread open and the optical fiber is fed into the interiorpassage 31 of the jacket through the slit 29. Filler is then injectedinto the slit. The slit is then allowed to self-close, and the cable iscollected at roller 329.

FIG. 15 illustrates an example fiber optic cable 420 in accordance withthe principles of the present disclosure. The fiber optic cable 420includes a plurality of buffered optical fibers 422, a plurality ofstrength structures 426 and a jacket 428. The jacket 428 includes arelatively large central passage 431 that runs along the length of thejacket 428. The optical fibers 422 as well as optional fillers arepositioned within the central passage 431. The jacket 428 also includesa slit 429 that runs along the length of the jacket for allowing thepost-extrusion insertion of the optical fibers 422 into the passage 431of the jacket 428. The jacket 428 further includes interior passages 433that run parallel to the passage 431 for holding the strength structure426. The components of the cable 420 can be constructed of the same orsimilar types of material described with respect to the embodiment ofFIG. 1.

The slit 429 is depicted having a V-shaped cross-section that provides anested interlock for mechanically holding the opposing surface of theslit in alignment with one another. In other embodiments, differenttypes of interlock configurations (e.g., hooks, latches, etc.) can beused. In certain embodiments, the fibers 422 occupy less than half thevolume of the passage 431 to facilitate movement between the fibersduring bending. In certain embodiments, the fibers are not in contactwith the surface of the jacket defining the passage 431. In certainembodiments, the fibers are not stranded. The passage is preferablyadjacent the center of the cable.

In one embodiment, the cable 420 can be manufactured by a processsimilar the process use to make the embodiment of FIG. 1. For example,the cable can initially be extruded through a crosshead, and then abundle of optical fibers can subsequently be inserted into the cableafter extrusion using an insertion system of the type shown at FIG. 12.

FIG. 16 shows an example crosshead 502 suitable for extruding the cable420 of FIG. 15. The crosshead 502 includes a jacket material inputlocation 500 that receives thermoplastic material from an extruder 504.A tip 602 and a die 604 are mounted at the crosshead 502. The tip 602defines a first inner passageway 606 through which a rip member 615 (seeFIGS. 16 and 17) is fed. The tip 602 also defines second and third innerpassageways 607, 611 through which the strength structures 426 are fed.The die 604 defines an annular extrusion passage 608 that surrounds theexterior of the tip 602. The crosshead 502 defines an annular passageway609 for feeding the thermoplastic jacket material from the extruder 504to the annular extrusion passage 608. Within the crosshead, the flowdirection of the thermoplastic material turns 90 degrees relative to theflow direction of the extruder 504 to align with the direction of travelof the strength structures 426 and the rip member 615.

Referring to FIG. 17, a slitting blade mount 620 is coupled to the die604. A blade 623 having a v-shaped cross-section is mounted to the blademount 620 at a location adjacent the exit of the crosshead 502. Theblade 623 functions to cut the predefined slit location for the slit 429into the jacket of the cable 420 as the cable exits the crosshead 502.After extrusion of the cable 420, the rip member 615 is pulled from thejacket to ensure that that the pre-defined slit location is opened toform the slit. Thereafter, the slit is spread apart to allow the bundleof optical fibers to be inserted into the central passage of the jacket.

Since many embodiments of the invention can be made without departingfrom the spirit and scope of the invention, the invention resides in theclaims hereinafter appended and the broad inventive aspects underlyingthe specific embodiments disclosed herein.

1. A system for manufacturing a telecommunications cable including astrength structure and a rip member embedded within a jacket of thetelecommunications cable, the system comprising: a cable jacket materialinput location; an extrusion crosshead, the extrusion crossheadincluding a tip having an exterior, the tip defining a first passagewayconfigured to receive the strength structure and a second passagewaygenerally parallel to the first passageway that is configured to receivethe rip member, the extrusion crosshead also including a die defining anannular extrusion passage that surrounds the exterior of the tip, theannular extrusion passage in fluid communication with the cable jacketmaterial input location; and a slitting blade configured for slittingthe jacket as the jacket exits the extrusion crosshead, the slittingblade configured to cut a slit within the jacket that extends completelyfrom an exterior of the jacket to the rip member.
 2. A system accordingto claim 1, wherein the tip defines at least a third passageway parallelto the first and second passageways, the third passageway configured toreceive a second strength structure.
 3. A system according to claim,wherein the blade has at least a portion including a v-shapedcross-section.
 4. A system according to claim 1, further comprising anextruder for providing cable jacket material to the cable jacketmaterial input location, the extruder including an extruder barrel andan auger/style extruder screw.
 5. A system according to claim 4, whereinthe extruder is positioned generally perpendicular to the annularextrusion passageway of the extrusion crosshead.
 6. A system formanufacturing a telecommunications cable including a rip member embeddedwithin a jacket of the telecommunications cable, the system comprising:a cable feed station and a cable take-up station, wherein the cable feedstation and the cable take-up station are configured to move the cablein a direction going from the cable feed station toward the cabletake-up station; a rip member removal station located between the cablefeed station and the cable take-up station, the rip member removalstation including a roller that pulls the rip member from the cable todefine a slit extending from an exterior of the jacket of the cable toan interior passage of the cable as the cable is moved between the cablefeed station and the cable take-up station; and a signal transmittingmember insertion station located between the rip member removal stationand the cable take-up station, the signal transmitting member insertionstation including a plow and an insertion tool, the plow configured tospread the slit as the cable is moved between the cable feed station andthe cable take-up station, the insertion tool configured to extend intothe interior passage of the cable for inserting the signal transmittingmember into the interior passage.
 7. A system according to claim 6,wherein the cable feed station includes a feed roller and the cabletake-up station includes a cable take-up roller.
 8. A system accordingto claim 6, wherein the signal transmitting member includes an opticalfiber.
 9. A system according to claim 8, wherein the signal transmittingmember insertion station includes a fiber feed roll for providing theoptical fiber and a pair of pinch rollers for pushing the optical fiberinto the insertion tool.
 10. A system according to claim 6, wherein theinsertion tool includes an angled signal transmitting member receivingportion and a bent tip, the bent tip configured to fit through the slitand into the interior passage and coaxially align with the interiorpassage.
 11. A system according to claim 6, further comprising a fillerinjection tool located between the signal transmitting member insertionstation and the cable take-up station, the filler injection toolconfigured to inject filler into the interior passage after insertion ofthe signal transmitting member therein.
 12. A method for manufacturing atelecommunications cable, the method comprising: extruding a cablejacket with a strength structure and a rip member embedded within thejacket, the cable jacket being extruded between a tip and a die; afterextrusion, slitting the jacket with a blade located adjacent an exit endof the die to provide a predefined slit location; after slitting,pulling the rip member from the jacket through the predefined slitlocation to provide an access location to an interior passage of thejacket; and inserting an optical fiber into the interior passage of thejacket through the access location.
 13. A method according to claim 12,wherein the step of inserting an optical fiber into the interior passageincludes inserting a bundle of optical fibers.
 14. A method according toclaim 12, wherein a slitting blade is used to slit the jacket.
 15. Amethod according to claim 14, wherein the slitting blade has a portionincluding a generally v-shaped cross-section.
 16. A method according toclaim 14, wherein the slitting blade cuts a slit that extends completelyfrom an exterior of the jacket to the rip member.
 17. A method accordingto claim 12, wherein the cable jacket includes at least two strengthstructures embedded within the cable jacket.
 18. A method according toclaim 12, wherein the cable jacket is relatively molten when being slitwith the blade.
 19. A method according to claim 12, further comprisinginjecting a filler into the interior passage after the optical fiber isinserted into the interior passage.
 20. A method according to claim 12,further comprising moving the jacket through a spreading station wherethe access location is spread apart to facilitate insertion of thesignal transmitting member into the interior passage.